package com.company.example.concurrent.lock;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/**
 * Created by ywl on 2017/2/15.
 */
public class MutexLock implements Lock{
    // 仅需要将操作代理到Sync上即可
    private final Sync sync = new Sync();

    // 静态内部类，自定义同步器
    private static class Sync extends AbstractQueuedSynchronizer {
        // 是否处于占用状态
        protected boolean isHeldExclusively(){
            return getState() == 1;
        }

        //当状态为0的时候获取锁
        public boolean tryAcquire(int acquires){
            if(compareAndSetState(0,1)){
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        //释放锁，将状态设置为0
        protected boolean tryRelease(int releases){
            if(getState() == 0) throw new IllegalMonitorStateException();
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }

        //返回一个Condition，每个Condition都包含了一个Condition队列
        Condition newCondition(){
            return new ConditionObject();
        }
    }
    @Override
    public void lock() {
        sync.acquire(1);
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1,unit.toNanos(time));
    }

    @Override
    public void unlock() {
        sync.release(1);
    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }
}
